<template>
  <div class="spec-preview">
    <img :src="imgObj.imgUrl"/>
    <div class="event" @mousemove="handler"></div>
    <div class="big">
      <img :src="imgObj.imgUrl" ref="big"/>
    </div>
    <!-- 遮罩层 -->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props:["skuImageList"],
    data(){
      return {
        currentIndex:0
      }
    },
    computed:{
      imgObj(){
      return this.skuImageList[this.currentIndex]||{}
      }
    },
    methods:{
      handler(e){
        let {big,mask}=this.$refs
        let minX=mask.offsetWidth/2//算出最小阀值
        let maxX=e.target.offsetWidth-mask.offsetWidth//算出最大阀值
        let minY=mask.offsetHeight/2
        let maxY=e.target.offsetHeight-mask.offsetHeight
        let X=e.offsetX
        let Y=e.offsetY
        X<minX? X=0 : X = X - minX
        X>=maxX?X=maxX:X
        Y<minY?Y=0:Y=Y-minY
        Y>maxY?Y=maxY:Y
        mask.style.left=X+'px'
        mask.style.top=Y+'px'
        big.style.left= -X*2+'px'
        big.style.top= -Y*2+"px"
      }
    },
    mounted(){
       //全局事件总线：获取兄弟组件传递过来的索引值
       this.$bus.$on('getIndex',(index)=>{
        //修改当前响应式数据
        this.currentIndex = index;
       })
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>